Field of the Invention
The invention relates to an arrangement for providing a vehicle, in particular a track bound vehicle and/or a road automobile, with electric energy, wherein the arrangement comprises a receiving device adapted to receive an alternating electromagnetic field and to produce an alternating electric current by electromagnetic induction (i.e. magnetic induction which is caused by an electromagnetic field and the induction produces electric energy). The receiving device comprises at least one inductance which is formed by an electrically conducting material for producing one phase of the alternating electric current by the electromagnetic induction. The at least one inductance and optionally at least one further electrical element (in particular a capacitance), which is connected (in particular in series) to the inductance in order to produce one phase of the alternating electric current, comprise(s) a resonance frequency at which the phase of the alternating electric current is produced if an alternating electromagnetic field of corresponding frequency is received by the receiving device. The inductance is connected to a rectifier for rectifying the alternating electric current and thereby producing a direct electric current. As a skilled person will know, the resonance frequency at which the phase of the alternating electric current is produced may vary depending on the inductive coupling between the receiving device and the device which generates the electromagnetic field.
Furthermore, the invention relates to a system for transferring energy to a vehicle, wherein the system comprises the arrangement, and relates to a vehicle comprising the arrangement. The invention also relates to a method of manufacturing the arrangement and to a method of operating a vehicle by means of a receiving device which receives an alternating electromagnetic field and produces an alternating electric current by magnetic induction.
Description of Related Art
WO 2010/031595 A2 discloses an arrangement for providing a vehicle, in particular a track bound vehicle, with electric energy, wherein the arrangement comprises a receiving device adapted to receive an alternating electromagnetic field and to produce an alternating electric current by electromagnetic induction. The receiving device comprises a plurality of windings and/or coils of electrically conducting material, wherein each winding or coil is adapted to produce a separate phase of the alternating electric current.
The present invention can be applied to any land vehicle (including, but not preferably, any vehicle which is only temporarily on land), in particular track bound vehicles, such as rail vehicles (e.g. trams), but also to road automobiles, such as individual (private) passenger cars or public transport vehicles (e.g. busses, including trolleybuses which are also track bound vehicles). Preferably, the primary side conductor arrangement which produces the alternating electromagnetic field is integrated in the track or road of the vehicle so that the electric lines of the primary side conductor arrangement extend in a plane which is nearly parallel to the surface of the road or track on which the vehicle may travel. As also described by WO 2010/031595 A2, the receiving device can be located at the underside of a vehicle and may be covered by a ferromagnetic body, such as a body in the shape of a slab or plate. A suitable material is ferrite. The body bundles and redirects the field lines of the magnetic field and therefore reduces the field intensity above the body to nearly zero. However, other configurations, locations and/or orientations of the primary side conductor arrangement are possible. For example, the primary side conductor arrangement may be located sideways of the vehicle.
In any case, the gap between the primary side conductor arrangement and the at least one inductance of the receiving device should be as small as possible, since the efficiency of the wireless energy transfer between primary and secondary side is smaller for larger gaps. For the same reason, the voltage which is induced in the at least one inductance depends on the size of the gap. One way to handle the varying voltage on the secondary side of the system is to supply the electric energy to power consumers only, which are voltage-tolerant, i.e. can be operated in a wide range of voltages. One example, to which the present invention can be applied, is the traction system of a rail vehicle which comprises a direct current intermediate circuit connected to the receiving device and which further comprises at least one inverter which inverts the direct current to an alternating current for operating at least one traction motor of the vehicle. The inverter can be controlled to compensate for voltage fluctuations in the direct current intermediate circuit.
However, there are other electric systems or devices in vehicles which cannot tolerate the varying voltage. A further possibility of providing the energy to the vehicle and using it is therefore to control the size of the gap between primary and secondary side inductances in order to keep the voltage fluctuations within a small range of voltages.
WO 2009/074207 A2 describes a system for contactless energy transmission to a part of the system, in particular a movably arranged part of the system, and a method, where a stationarily installed primary conductor is provided to which one or several secondary coils enclosed by said part are inductively coupled. The secondary coils are connected in series with one or several capacitors such that the resonance frequency of the thus formed series resonant circuit is essentially equal to the frequency of an alternating current injected into the primary conductor, wherein the voltage occurring at the series resonant circuit is fed to a rectifier, on the output side of which a switch is provided which can be actuated as a short-circuiter, the current not passing through the switch being fed to a smoothing capacitor via a free-wheeling diode and the voltage occurring at the smoothing capacitor being made available to a user.
A disadvantage of this secondary side arrangement is the free-wheeling diode which increases losses during operation. Furthermore, the embodiment shown in FIG. 1 of WO 2009/074207 A2 has the disadvantage that an electric current always flows through a series connection of two semiconductors, namely the free-wheeling diode and one of the diodes in the rectifier and consequently, electric losses are increased.